(a) Field of the Invention:
The present invention relates to an automatic rhythm apparatus, and more particularly it pertains to an automatic rhythm accompaniment apparatus having an improved tone generating unit which produces rhythm tones with variable timbres of the same instrument according to tone levels.
(b) Description of the Prior Art:
In the conventional automatic rhythm accompaniment apparatuses, there is known the tone generating circuitry which is so arranged that the tone waveshape for a plurality of cycles of a percussion tone produced from each kind of percussion instrument (typically, the whole waveshape of a percussion tone ranging from the attack through to the end of decay) is A/D-converted and the resulting waveshape data is stored in a memory, and that the stored waveshape data is read out from the memory to reproduce the percussion tone.
Also known is the art that an apparatus arranged so that the tone volume (levels) of the reproduced tones are increased at specific beats in order to add an accent to the rhythm tone performance.
According to such prior art arrangements as mentioned above, there has been the problem such that, in case the tone volume (levels) of the reproduced tone is to be controlled for the purpose of, for example, adding an accent to the rhythm, there is not obtained a variation of tone color of the rhythm tone being reproduced, although there may be obtained a variation of the tone volume thereof, and that accordingly the reproduced rhythm tones lack natural feeling. More particularly, in natural percussion instruments, there develops a difference in waveshape between a hard percussion tone (strongly struck tone) and a soft percussion tone (softly struck tone) as will be exemplarily shown in FIGS. 1 and 2 with respect to a "tam-tam" drum, and the tone color is noted to show a variation along with the tone volume. However, in conventional automatic rhythm apparatuses, there has not been obtained such a variation of tone color. It should be noted here that, although the waveshape shown in FIGS. 1 and 2 is produced, actually, in a continuous form throughout the period of time t.sub.1 .about.t.sub.7 or t.sub.1 '.about.t.sub.7 ', but the waveshape is illustrated here in divided fragments for the convenience of depiction.
In general, in order to realize a variation of tone color of a percussion tone in compliance to the level of the tone volume or loudness thereof, there may be considered such a technique that a number of different waveshapes corresponding to the various different intensities of percussion per percussion instrument are stored respectively in memory means, and that an optimum waveshape is selected in compliance to the level of the tone volume which is desired to be read out. Such an arrangement of apparatus, however, gives rise to the inconveniences that the capacity of the memory means naturally becomes tremendously large and that, accordingly, the apparatus as a whole unavoidably becomes complicated and costly.